The invention relates to fluid filters, including cylindrical air filters.
Cylindrical filters with parallel flutes are known in the prior art, for achieving high contaminant holding capacity. The inlet of such filters can become clogged due to edge phenomena. For fluid in motion, the flute edges are solid obstacles around which the fluid moves in a manner similar to the way air moves around a jet""s wings. However, contaminant particles may be captured by the same edges due to the inertial mechanism. Because adhesive forces between the collected particles are usually greater (since they are formed of the same material) than those between the flute edge and particles, large clusters of particles are formed on previously captured contaminant. These growing particle clusters can clog the flutes. Moreover, the relatively large sealed inlet area of the flutes increases flow restriction. The increased initial flow restriction prevents high contaminant holding capacity from being obtained.
In the present invention, contaminant accumulation on the inlet face is significantly reduced. Contaminant holding capacity of the present invention increases due to a more uniform flow field and enhanced utilization of filter media surface. Since the sharp pleat inlet edges have low restriction to fluid flow, contaminant capacity increases further. Moreover, contaminant will not clog the filter inlet because there are allowable contaminant passages around the individual filter elements. The contaminant cake is distributed more uniformly along the entire filter, and filter pressure drop increases more slowly, increasing filter life.
The multi-element cylindrical filter with equalized flow in accordance with the present invention provides a more compact sized filtration system. The new design enables utilization of nearly the entire volume of the filter housing for filtration. The unit volume contaminant capacity is greater since the inside volume of the filter is filled with filter medium rather than being left empty as in previous designs. Cylindrical or slightly conical filter elements of pleated filter media use alternating seal technology. The layers of elements are concentrically arranged, and a gap is provided between elements.